This invention relates to a pacemaker with patient effort-controlled frequency, more particularly to a rate adaptive pacemaker that adjusts the stimulating frequency in accordance with the patient's physical effort.
It is known that the effort exerted by a patient can be monitored based on a measure of acceleration along an axis, e.g., a vertical or antero-posterior axis. An accelerometer placed on the patient's trunk provides a signal that enables one to obtain an approximation of the energy expended for the patient's dynamic efforts. There is a good correlation between the integral of the absolute value of the signal of acceleration along the vertical axis, for instance, and the energy expended by the patient. Computation of this integral for set periods of time provides an image of the power supplied by the patient in dynamic efforts, which can be selected as a control parameter for controlling the heart rate. See, e.g., U.S. Pat. No. 4,926,863, which describes a rate-responsive cardiac pacemaker with the pacing frequency controlled based on acceleration measured along an antero-posterior axis.